In a flexible antagonist protocol, earlier, criteria-based initiation of GnRH antagonist is associated with increased pregnancy rates in IVF

BACKGROUND: The purpose of the study was to assess ongoing pregnancy rates across groups of patients treated by IVF, which were defined according to criteria aimed at the prevention of premature LH surge and used for initiating GnRH antagonist. METHODS: This is a prospective observational cohort study. During the last 3 years, in IVF-ICSI patients undergoing controlled ovarian stimulation (COS) with the antagonist protocol, the antagonist administration was initiated according to at least one of the following patient-specific criteria: (i) at least one follicle measuring > 14 mm; (ii) estradiol levels > 600 pg/ml; and (iii) LH levels > 10 IU/l. Based upon these criteria, 208 cases of normal responders were analysed and categorized into three groups according to the starting day of the regimen: group D4 (n=40) for day 4, group D5 (n=98) for day 5 and group D6 (n=70) for day 6. The main outcome measure was the ongoing pregnancy rate per started cycle. RESULTS: The total number of patients in the D4 and D5 groups (138 out of 208), who received the antagonist earlier, was considerably larger compared with that of D6 (70 out of 208). Ongoing pregnancy rates were 37.5, 34.7 and 18.6% for groups D4, D5 and D6, respectively. Patients who initiated the GnRH antagonist on days 4 and 5 had statistically significant higher pregnancy rates compared with day 6. Rapid response, causing earlier antagonist administration initiation, according to the proposed criteria for the prevention of premature LH surges, and the absence of premature luteinization, as evidenced by normal progesterone levels on HCG day, were found to be independent positive predictive factors for favourable IVF outcome. CONCLUSIONS: The employment of an algorithm of criteria, aimed at the prevention of premature LH surges in a flexible antagonist protocol, resulted in antagonist initiation earlier than on stimulation day 6 in a significant proportion of patients. In those patients, a higher pregnancy rate was observed.